Sling Hardware

How to remove Rust/Corrosion from black brass?

I got a M1 Carbine sling (Original WWII Sling),and it has lots of rust and corrosion on its tabs and other hardware. The hardware is all brass, with a black coat on it. Without destroying the finish (black coat), or much of it, how can I remove the rust/corrosion with as little of the brass color showing as possible?

Thanks

Do nothing to it to try to pretty it up, you will only devalue it the Original patina is worth more than restored.